While installing an electric wiper conversion in my 59 today I also installed a new temperature sending unit as my gauge wasn't working. It seems to be working now but after letting it idle in the driveway the needle is pretty far to the right, not to the dot but pretty close. I don't have a fan shroud, not sure if it came with one, is this normal? The thermostat seems to be opening, plenty of coolant. I assume it should run cooler going down the road.

Did it boil over when you removed the cap after shutting it off? Is the radiator in the stock 6 location? When I put in my first V8 it ran hot with the radiator in 6 location. Added a shroud and it worked a lot better. If you are running a stock radiator make sure the cap is 7#.

Stock 235 I6, it didn't boil over or even smell hot. I am wondering if I should also replace the gauge, it didn't work at all before which is why I replaced the sending unit. While running the gauge shows hot, if I cut it off and turn the key back on it is slightly above midway.

Make absolutely sure that it is the exact sender for your application and the gauge you are running. I just went thought that on my 77 The temp always read low so I ordered a new correct for the application Delco sending unit and it showed hot. I did swap the 195 thermostat that came with the truck for a 180 and now it runs with the needle pointing straight up on the gauge. I'm swapping radiator and all hoses in a couple of days when the 4 core gets back from the radiator shop and will get the heat gun out then.

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Founding member of the too many projects, too little time and money club.

My ongoing truck projects:
48 Chev 3100 that will run a 292 Six.
71 GMC 2500 that is getting a Cad 500 transplant.
77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.

for sure get a manual reading on the engine for comparison. those digital heat guns are pretty cheap these days. a good old fashioned meat thermometer in the rad cap hole or placed on the thermostat housing may also give a decent indication if you don't wanna spend the cash on a digital one to check temps at the thermostat housing.
it is pretty common for a thermostat to wear out some and the movable part will rub on the stationary part and can end up not opening fully or not closing fully sometimes, depending on how it sticks. also, some of the aftermarket thermostats are not worth the powder to blow them. I usually try to stick with OEM only thermostats for this reason. you also may want to remove the cap, when cold, and have a look at the ends of the rad tubes. some coolant may need to be drained for this. look for blossoming around the ends of the tubes. this indicates some occlusion of the rad (plugging and causing poor flow and heat dissipation) from calcium or deposit build up inside. also, engines may run hot if the water pump isn't pumping like it should due to debris in the impeller or partially eroded impeller which can be caused from coolant that hasn't been flushed in a long time. the PH level of the coolant can change and cause corrosion. also, look for debris in the rad fins or anything else that may occlude air flow through the rad.
just a couple of thoughts to consider